Venus Returns At Dawn / Sun Gets Busy

Welcome back, Venus! You can see our new “morning star” in the east about 40 minutes before sunrise. Venus moves away from the sun, rising higher, in the coming days and weeks. Created with Stellarium

Back so soon? Venus, lately of the evening sky, has returned to view in the morning sky after speeding north of the sun during conjunction on March 25. The transition from morning to evening is swift because the planet is between the Earth and sun and relatively close to us — about 26 million miles. Its proximity means it appears to move faster and cover more ground, swinging from one side of the sun to the other in a hurry. Just like an airplane that takes off in front of you compared to the same plane 25 miles away and 35,000 feet high, the closer something is, the faster its appears to move.

Just the opposite happens when Venus transitions from morning back to the evening sky. Then, the brilliant planet lies on the opposite side of the sun from Earth. It’s much further away — 158 million miles — and appears to move much more slowly, taking weeks to “separate” from the sun and finally show in the west after sunset.

As Venus orbits the sun, it catches up on the slower Earth and passes it. Right now, we see Venus a week past inferior conjunction — it’s located a short distance to the right of the sun in the morning sky. Credit: ESO with annotations by the author

To see Venus now, you need only face east about 35-45 minutes before the sun comes up and watch for a single bright star against the twilight glow. Be sure you pick a place with a good eastern horizon. Bring binoculars and you’ll see the planet as a wiry crescent. The crescent has reversed direction compared to its evening appearance. Its horns point west instead of east.

Venus and Mercury both never get too far from the sun. They can’t because they both lie inside Earth’s orbit. They may swing east or west of the sun but neither planet can get around behind us. Only a superior planet can do that. Don’t mistake Mars, Jupiter and the rest for snobs based on that description. That’s what astronomers call all planets that orbit beyond the Earth. Superior planets can line up behind the Earth in this order: sun-Earth-planet. When that happens, the planet is directly opposite the sun in our sky: it rises at sunset, stays up all night and sets at sundown. No, I’m afraid Venus and Mercury can’t do that.

The next planet to line up behind Earth at “opposition” will be Jupiter on April 7. Already, it’s up in the east around 9:30 and really looks fantastic around midnight high in the southeastern sky.

After weeks of doldrums and next to zero sunspots, the sun has come back to life with three nice groups on display. Departing region 2644 (upper right) has cooked up four moderately strong M-class flares in the past few days. Sunspot region 2645 spans some 93,000 miles (150,000 km). See below for a different view of region 2645. This photo was taken by NASA’s Solar Dynamics Observatory on April 2. Credit: NASA/SDO

The sun illuminates all the planets, making them visible to the eye and telescope. Throw a giant invisibility cloak over our star and the planets would disappear from view … unless you had an infrared telescope, which “sees” an object through the heat it emits. Heat is simply another form of light. A radio telescope could also spot the planets, radio being yet another form of light.

Sunspots have a north pole and a south pole just like a magnet. Other times they have multiple north and south poles within the same group. Region 2645 has a beautiful N-S magnetic field which causes the material around it to line up along the group’s magnetic field lines much like filings around a simple bar magnet (left). Credit: NASA

Speaking of heat, the sun’s the hottest thing in the neighborhood and has recently been shooting off some powerful flares. Energetic ultraviolet light and X-rays’ effects on our upper atmosphere have caused occasional shortwave radio transmission blackouts here on the planet. But it’s unclear at this point whether auroras might result from the activity. Likely not as all the flares were directly off the sun’s edge and away from the Earth. Photos of the two big sunspot groups but especially region 2645 clearly show them strutting their magnetic stuff with material arranged around them just like iron filings around an ordinary bar magnet but on a grand scale.

Both the filings and ionized (electrified) gases in the sun’s atmosphere arrange themselves in the shape of the magnet’s magnetic field with a north pole on one end and a south on the other. How interesting to see something familiar play itself out across tens of thousands of miles on a star 93 million miles away.

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8 Responses

caralex

I hadn’t thought about the speed with which Venus changes from morning to evening star, and vice versa. Interesting information! What I HAD wondered about, is the length of time from conjunction to greatest elongation, either eastern or western, and back to conjunction. Are these intervals the same length, or is one shorter than the other?

The reason I asked is because I was wondering if there was a sort of ‘lag’ effect. We’re travelling in the same direction as Venus, so I thought one period of time might be shorter than the other.

I had in mind the effect we see with Mars, where Mars seems to linger in the evening sky for months and months after opposition, getting fainter and fainter, yet still remaining visible, when you’d think it should have gone behind the sun months earlier. It’s caused by Mars just about staying visible from Earth on the same side as the sun, so I thought something similar might be happening with Venus.

I don’t know if I’ve explained this very well – I can see it in my mind’s eye, but can’t put it into words!

Well, I found a way to do some calculations, using the information on Heavens-Above.com. It seems that it takes 70 days to get from Inferior conjunction to Greatest Western Elongation, 220 from there to Superior conjunction, another 221 to Greatest Eastern Elongation, and 70 to Inferior conjunction.

So there IS a noticeable difference when Venus is on this side of the sun than on the far side. As I only really notice Venus in the evenings, I’ll use that apparition only. It appears that it takes longer to get from behind the sun to it’s greatest evening showing, than it does to fall back to the sun again – seven months versus only two months. When it goes, it goes very quickly, as it did a few days ago!